Coloring agents are commonly used as additives in the manufacturing of food products, pharmaceuticals and hygienic products. Commercial coloring agents can be synthetic substances which are normally referred to as dyes or azodyes, or the agents can be pigments of natural origin, e.g. in the form of plant material containing the pigment or as more or less purified pigments extracted from plants, animals or microorganisms. Occasionally, food grade or pharmaceutically acceptable coloring agents are provided in the form of synthetic or artificial substances having the same chemical composition as naturally occurring pigments. These types of coloring agents are also referred to in the art as natural identical colors. However, in the present context the terms “natural compound” and “natural pigment” are used exclusively to designate compounds and pigments which are derived from natural sources.
Many natural organic pigments have some common chemical properties, relating to the conjugated systems of carbon-carbon double bonds with or without heteroatoms, that provide the conjugated pi electron systems with low energy excitation states that absorb visible light and render those compounds their color.
Other types of compounds that may be found and isolated from natural sources include natural flavorings, nutrients and pharmaceutical compounds.
Astaxanthin is a carotenoid compound found mostly in animal organisms but also in yeast, plants, algae and microorganisms. This compound and other related carotenoid compounds give the reddish hue to many crustacean species and to their natural predators such as salmon, trout and related species. However, astaxanthin is not naturally present in typical feed sources used in the aquacultural production of such fish species. It is typically added to feed compositions to render the fish its natural color to increase consumer appreciation and market value.
Astaxanthin has also been used as a nutritional supplement for humans, based particularly on its properties as a powerful antioxidant. A growing body of scientific evidence demonstrates that the antioxidant properties of astaxanthin surpasses those of vitamin C, vitamin E, beta-carotene, and other carotenoids.
Synthetic astaxanthin is commercially available but at a high cost. The related carotenoid compound canthaxanthin can be used as a substitute but does not provide as high quality products. Various methods for isolating astaxanthin from natural sources have been suggested such as by extraction with edible oils at high temperatures (U.S. Pat. No. 3,906,112; U.S. Pat. No. 4,505,936), using organic solvents such as carboxylic acid alkyl esters (EP 077,583), chloroform (JP 118,226), or solvent mixtures (JP 11,049,972); boiling lye (U.S. Pat. No. 5,210,186), and hydrochloric acid (JP 9,301,950), and also by enzymatic methods (e.g. CA 1,313,835) where carotenoproteins are extracted with proteases from uncooked shrimp Waste (shells, heads, claws, etc. from shrimp pilling)
The present invention provides a method for isolating astaxanthin and other organic, primarily hydrophobic compounds including other carotenoids from liquid media by adsorption on to a natural substrate comprising fish scales. The method is useful for isolating and concentrating natural compounds such as natural pigments from a solution and the inventors have found that astaxanthin that is present in the run-off water from crustacean processing can be adsorbed by the method and utilized. The method can similarly be used to recover astaxanthin that has been separated from shellfish waste.
The fish scales with the adsorbed compound act in-the way to-stabilize the-adsorbed compound, e.g. pigments like astaxanthin which are susceptible to deterioration due to oxidation, heating and exposure to light.
The fish scales with the adsorbed compound can be used as a direct source of the compound, and or the compound can be separated from the scales with appropriate means.